In a power transmission apparatus of a vehicle, a clutch is provided for transmitting the driving power of the engine in response to the driving requirement.
One example of a known clutch is the wet type friction clutch, which has an end plate (clutch disc) connected to an input shaft, a pressure plate, and a friction plate connected to an output shaft and placed between the end and pressure plates. The pressure plate is operated by the pressure of clutch operating oil, and the friction plate is clamped between the end plate and the pressure plate, so that driving power is transmitted from the input shaft to the output shaft by the frictional engagement of the friction and end plates. A cooling apparatus is provided which feeds cooling oil to the portion of the friction plate which is clamped between the end and pressure plates.
A cooling apparatus for a clutch is disclosed, for instance, in Japanese Patent Laid Open Publication Gazette No. Sho-62-151664. This publication discloses cooling a clutch during its half clutch (high slippage) state when the heat generated is great.
Generally, in a cooling apparatus for a clutch, a hole is formed at the core of the input shaft, and oil is supplied through this hole so as to flow on the surface of the friction plate due to centrifugal force.
However, in the conventional clutch cooling apparatus, the clutch was cooled only in a half clutch state when much heat is generated, and was not cooled in the time either during running or not using the clutch, or during intermittent use when use of the clutch is frequently repeated as on rough and coarse roads and the like. Thus, the clutch temperature became high, whereby wear and seizing was produced, resulting in a disadvantage that the useful life of the clutch becomes shorter.
Therefore, the present invention relates to a clutch cooling apparatus for a stepless variable speed transmission capable of extending the useful life of the clutch by effectively cooling the clutch by providing a first clutch cooling means for cooling the clutch upon a predetermined running of the vehicle, and a second clutch cooling means for cooling the clutch during the driving of the engine irrespective of the running condition of the vehicle.
To accomplish the above, a stepless variable speed transmission according to the present invention includes a clutch for transmitting the driving power of the engine from an input shaft to an output shaft by clamping a friction plate between a pressure plate and an end plate connected to the input shaft, a first clutch cooling means for cooling said clutch in the time of predetermined running of said vehicle, and a second clutch cooling means for cooling said clutch during driving of said engine irrespective of the running condition of said vehicle.
According to the preferred construction of the present invention, the clutch is cooled during the time of predetermined running of the vehicle, for instance, during the half clutch state associated with starting motion of the vehicle, by a first clutch cooling means, and is simultaneously cooled constantly during engine operation by a second clutch cooling means. Consequently, since the clutch can always be surely cooled, generation of the high clutch temperature or seizing of the clutch is avoided even if intermittent use of the clutch is repeated. Hence, the useful life of the clutch can be extended.